Seeking consult with dentist expert in signs and symptoms of newly placed composite filling failure (2 molars and counting), range of effects on affected teeth and gum; recommendations on selecting a dentist for redo. See/search for "QPart1" for more?

See below. Why do you feel that these restorations need to be redone? Sensitivity is normal and transient with many restorations. There are many variables to cause sensitivity including the depth of the restoration. Speak with your dentist or call a dental school in your area for a non-biased second opinion.
Sorry to hear that. There are a myriad of different factors that can contribute to early composite failures. There could have been issues when the composites were placed, there may have been hygiene issues in maintaining the composites, etc... The possibilities are vast. I recommend finding a dentist who you trust and who you feel is doing good work. If you're in the NYC area then feel free reach out to me!
Prob with composite. Composite restorations (white fillings) are much more technique sensitive to place than other restorative materials. The area needs to be well isolated and the bonding agents need time to react with the tooth before adding the filling material. The material needs to be cured completely with the light. You may want to look for dentist that is a Fellow or Master in the Academy of General Dentisty.
Composite fillings . Need more information: why do you think the fillings failed; how long ago were the teeth restored; are you having pain to hot, cold, or chewing; did the teeth fracture? Have you returned to your dentist to have the problem corrected?